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Biomedical subjects

A Kantrowitz

Publications and source records attributed to A Kantrowitz.

At least 37 records · Page 2Linked to original sources
PubMed1983

A method for generating obstructive thrombi in the coronary arteries of the conscious dog.

A technique for staging the generation of obstructive thrombi in the coronary arteries of conscious dogs is described. At thoracotomy, electrodes are placed in the lumina of coronary artery branches. When thrombus generation in proximity to the intraluminal electrode tip is desired, anodal current is applied to the exteriorised end of the electrode. In each of nine anaesthetised adult mongrel dogs two to seven intracoronary electrodes were implanted for a total of 35. One to 75 days later, 50 to 800 microA anodal current was applied to 16 electrodes for 30 min to 48 h. Upon autopsy, thrombi in various stages of organisation were found in proximity to the intracoronary portion of 15 electrodes. Six electrodes were found to be damaged or broken. In contrast, only four of the 13 control electrodes were sites of thrombus formation. In seven dogs tissue sections indicated either myocardial ischaemia or infarct in regions whose perfusion was blocked by thrombi. This method may provide for discretionary generation of intracoronary thrombi in the desired quantity, at the preferred site(s), at selected times of onset. Consequently, it offers the possibility of adjusting the onset, severity, and time course of myocardial ischaemia.

Animals↗
PubMed1980

A prosthetic myocardium for repair of localized defects of the left ventricle: concept and hemodynamic feasibility.

As an approach to the treatment of patients with large but circumscribed akinetic or dyskinetic regions in the left ventricular myocardium as sequelae of acute myocardial infarction, excision of the defect and implantation of a mechanical functional equivalent of myocardium is suggested. Experimental investigation of this technique is described. Hemodynamic data from a series of dog experiments indicate that activation of the prosthetic myocardium after excision of the left ventricle is followed by improvement in various hemodynamic parametres of interest. Although substantial experimental work must be completed and difficult bioengineering problems solved, preliminary results have encouraged us to continue our investigations of the prosthetic myocardium. An imposing array of treatment methods is now available to the clinician who must deal with the sequelae of acute myocardial infarction. Selecting from pharmacologic, electrophysiologic, and surgical approaches the physician can in many instances design a treatment plan precisely tailored to the clinical problem. Large left ventricular aneurysms and their functional equivalents of ventricular dyskinesis or hypokinesis continue, however, to represent a class of problems in which established techniques have been less than satisfactory. Surgical excision with closure of the defect is regarded as effective for small aneurysms, but such procedures may so compromise cardiac output in patients with large ones as to be unacceptable. Unfortunately, it is just the latter group in which medical palliation is least likely to be effective in managing congestibe failure, angina, and other pathophysiologic manifestations. A relatively unusual approach derived from in-series techniques of mechanical assistance to the failing circulation (1) offers the theoretical possibility of a treatment tailored to the problem of a large ventricular aneurysm. Experimental investigation of this technique in the Surgical Research Laboratory at the Sinai Hospital of Detroit has progressed to the point that a report of our experiences to date may be of interest.

Animals↗
PubMed1978

Biocompatibility tests of components of an implantable cardiac assist device.

A permanently implantable in-series left ventricular assist device, the dynamic aortic patch (DAP), has been tested in chronic animal experiments. The DAP replaces a section of the intrathoracic aortic wall. Hemothorax and hematocele at the implantation site have been complications in recent experiments. Primary postoperative hemorrhage was ruled out, and the biocompatibility of all components was therefore examined. Dacron velour, Teflon felt, conductive polyurethane, segmented polyether polyurethane, and Teflon-coated polyester fiber sutures were implanted in the pleural cavities of dogs and tested in vitro by culturing canine saphenous vein explants on them. In vivo experiments demonstrated that all components elicited mild to moderate inflammatory reactions, but hematocele occurred only when the components were implanted in the aorta with direct blood contact and exposed to arterial blood pressures. In vitro, cells were cultured on all components with no signs of toxic reactions. These results indicated that the host tolerated all implant components without major inflammatory responses. However, histological data indicated that chronic slow bleeding into or through the Dacron velour in contact with the arterial blood serum could account for hemothorax or hematocele formation. Therefore, a configuration of the assist device using materials impermeable to blood may obviate these difficulties.

Animals↗
PubMed1976

An extravascular left ventricular assist device.

The hemodynamic efficacy and prosthesis-vessel interaction of a pneumatically activated circulatory assist device was investigated in 12 acute and 12 chronic studies in dogs. A polyurethane balloon encased in Dacron-velour cloth was fastened to the descending thoracic aorta with a spiral wrapping of Dacron graft material. Diastolic augmentation was provided by rhythmic inflation and deflation of the balloon. Hemodynamic results, based on 5 dogs with experimental myocardial ischemia, showed that left ventricular systolic peak pressure decreased by 8.2 +/- 1.9%, cardiac output increased by 13.1 +/- 2.8%, and circumflex coronary artery flow rose by 17.5 +/- 2.5%. In the chronic experiments the prosthesis was asynchronously but continuously activated from one to sixteen weeks at 74 cycles per minute. Postmortem examination of the implantation site in all 12 dogs showed that necrosis had developed but was limited to the outer half of the medial layer beneath the pumping chamber and that the aortic wall was compressed to about 70% of its original thickness. Although the method described represents a simple form of providing ventricular assistance, its applicability for long-term circulatory support remains to be evaluated.

Animals↗
PubMed1976

Challenge to conventional treatment for myocardial failure-mechanical assist.

Use of a prosthesis for temporary or permanent circulatory support in left ventricular failure has been investigated by our group for over 12 years. Experiences with both a U-shaped mechanical auxiliary ventricle (MAV) and the intraaortic balloon pump showed that in-series devices can stabilize the failing circulation. Studies with a MAV based on the balloon pump, the dynamic aortic patch (DAP) indicated that this system too is hemodynamically effective. In addition, data from extensive in vivo studies indicated that when its intravascular surface is made of Electrolour (Dacron velour backed by polyurethane with a negative electrical charge), the frequency of thromboembolism is greatly diminished. Following initial activation of the DAP in a patient with advanced chronic congestive failure, his hemodynamic parameters rapidly approached normal values: mean pulmonary artery and end-diastolic pressures were reduced, cardiac output increased, and myocardial metabolism changed from anaerobic to aerobic. The patient's cardiac function gradually improved, allowing his return to his home. The patient died on the 96th postoperative day after three months of improved cardiac function. Autopsy disclosed the DAP to be functional. A stable fibrin layer had formed on its intravascular surface; there were no signs of embolization. The DAP represents a promising approach to long-term ventricular support. For more than twelve years, our group has been interested in the possibility of using a mechanical prosthesis, not for total heart replacement, but rather for partial temporary or permanent circulatory support. In the first several years of work following this approach, we concentrated on the development of a permanently implantable system for in-series ventricular assistance. This work led to the study of several configurations of a mechanical auxiliary ventricle which gave effective circulatory support in laboratory and clinical studies [1,2]. The problem of achieving satisfactory interaction between blood and prosthesis was not resolved in these studies, but we were sufficiently encouraged by the hemodynamic effects to look into the possibility of working with the temporary support system initially proposed by Moulopoulos, Topaz, and Kolff [3].

Animals↗
PubMed1976

Hemodynamic effects of venous valves in aorto-coronary bypass grafts.

Use of the saphenous vein in aorto-coronary bypass surgery for treatment of occlusive coronary artery disease is a well-established technique. Use of the mammary artery for the same purpose has also been favorably reported. This study was undertaken to determine whether a vein graft containing a valve would have an added advantage. A comparison of the effect of competent and incompetent valves in vein grafts on the hemodynamics of coronary circulation was made. In a group of 18 dogs, a 5 cm. portion of each dog's cephalic vein containing a valve was used in a single aorto-coronary bypass graft. Flow measurements were made between the valve and the anastomosis of the graft to the left anterior descending coronary artery (LAD). The valve was made temporarily incompetent by the insertion of a spring wire basket, 3.5 mm. in diameter, through the valve via a side branch. The flow of blood through the venous graft with the competent valve was 11.0 +/- 2.6 per cent higher than with the incompetent valve. An analysis of flow patterns showed that this increased flow could be attributed to a reduction of backflow during systole and an increase in forward diastolic flow. Results suggest that postoperative myocardial perfusion is enhanced by the presence of valves in aorto-coronary bypass vein grafts.

Animals↗
PubMed1976

Permanent in-series cardiac assistance with the dynamic aortic patch: Blood-prosthesis interaction in long-term canine experiments.

The blood-prosthesis interaction of the dynamic aortic patch (DAP), an in-series assist device for permanent circulatory support which is implanted in the descending thoracic aorta, was studied in 65 long-term experiments. Periods of postoperative observation with the device inactive or activated ranged from 2 weeks to 22 months. The intravascular surface of the DAP, fabricated of Dacron velour backed by bioelectric polyurethane, displayed various degrees of organization, ranging from a thin fibrin layer to a well organized pseudointima. Activation of the system did not prevent the development of an organized pseudointima. Changes in free-plasma hemoglobin were minimal; platelet count per square millimeter and state of reactivity remained within normal limits. Evidence of renal embolization, attributable to activation of the device, was found in five animals. Frequent lethal complications were aortic rupture and infections of the thoracic cavity originating at the implantation site. Further improvement of the DAP and the techniques of implantation is indicated to insure its efficacy during long-term implantation and activation.

Animals↗
PubMed1976

Neuropathy in the upper extremity after open-heart surgery.

Eleven patients with upper-extremity neurological abnormalities underwent open-heart surgery performed through a median sternotomy incision. Seven of the 11 patients were referred in the routine manner to evaluate and treat the neurological problem. The remaining four were part of a consecutively studied group of 11 patients examined prospectively to determine the possible presence of abnormalities. Two of these four patients were asymptomatic. All lesions could be postulated to occur within the brachial plexus, the most common area being the median cord, but lesions were also noted in the posterior and lateral cords and upper trunk. The etiology of the problem appears to be stretching injury of the brachial plexus from retraction of the sternum, which in turn causes retroclavicular displacement of the clavicle. However, it is possible that an ischemic neuropathy could result from intraarterial procedures in some of our patients. The possibility that neurologic deficit may occur in the upper extremity should be considered by physicians who may have the opportunity to evaluate patients who undergo open-heart surgery.

Adult↗
PubMed1975

Patient selection for cardiac surgery in left ventricular power failure.

Nineteen patients in acute left ventricular power failure following acute myocardial infarction were given support with intraaortic balloon pumping and underwent cardiac catheterization. Hemodynamic response to disastolic augmentation, results of left ventriculography, and observations of selective coronary arteriography were evaluated to determine which patients could survive without operation, which would require operation to survive, and which could be predicted not to survive operation. Of ten patients who underwent operation, three were long-term survivors. Two patients predicted to have a good prognosis without surgery did survive. Of three patients who had been determined to require operation but not undergo it, two died in the hospital and one a month later. The four patients whose conditions were considered inoperable died in the hospital. The results indicate that current methods of predicting the need for corrective surgery are relatively accurate and that the rate of survival in surgically treated patients may be increased.

Assisted Circulation↗
PubMed1975

Simplified circular aortotomy in aortocoronary bypass operations.

Adaptation of a rongeur technique facilitates aortotomy in aortocoronary bypass operations. A single motion with a double-action duckbilled rongeur produces a smooth-walled, symmetrical aortotomy which varies in shape predictably according to the angle at which the rongeur is held relative to the axis of the aorta.

Aorta↗